1. Field of the Invention
The present invention relates to centrifugal clutching devices that are driven by a horizonal engine shaft that carries a clutch housing having a sprocket for driving a chain that engages the rear sprocket mounted to a wheel or axle of a powered cart. Even more particularly, the present invention relates to an improved centrifugal clutch apparatus for use on small motorized carts (or "karts" as they are called in the art) such as racing karts, go-karts, fun karts and the like wherein a clutch hub fits a horizontal drive shaft and rotates therewith, the hub providing a backing plate member with struts for supporting a plurality of arcuate wear pads, a plurality of coil springs extending from the wear pad toward the clutch hub, and an annular ring being mounted to "float" about the clutch hub, and the floating ring providing openings for attaching the coil springs thereto. The apparatus provides improved control of heat transfer between the engine, the engine drive shaft, and the critical parts of the clutch including the coil springs.
2. General Background
Small powered carts ("karts") are well known in the art as "racing karts", "go-karts" or as "fun karts" These small powered carts are typically powered by a three to ten (3-10) horsepower internal combustion engine having a horizonal drive shaft. Power from the engine is normally transferred through the drive shaft to a clutch shoe assembly that rotates with the drive shaft. The drive shaft and clutch shoe assembly are affixed using a key and a keyway for example. A publication that features such small karts and "karting" in general is the magazine entitled National Kart News, published monthly. National Kart News carries advertisements for numerous parts including various clutch products. Another monthly publication that contains clutch product advertisements is Kart Marketing International.
The clutch shoe assembly supports a plurality of wear pads that are held with a spring or springs in a non-engaging position when the engine is at idle speed. When the user depresses the accelerator pedal of the cart, the increased rotational speed of the engine drive shaft produces centrifugal force that urges the wear pads away from the engine drive shaft, into engagement with a clutch housing. The clutch drum housing has an annular surface that is adapted to receive the wear pads when they expand.
Typical go-kart, racing kart or fun cart clutches provide an external sprocket that drives an endless chain connected to a similar sprocket on the axial or wheel of the vehicle. Thus, when the user is at idle speed, the clutch drum housing is disengaged, and engine drive shaft are and the shoe assembly rotate independently of the clutch drum housing. The clutch drum housing is maintained in a static position because of the sprocket and chain engagement between the clutch housing and the rear sprocket.
When the user of a go-cart or a fun cart presses the accelerator, centrifugal force expands the wear pads away from the rotational axis of the clutch hub. This causes the clutch wear pads and the wear surfaces of the clutch wear pads to bear against an annular surface on the clutch drum housing. Once sufficient centrifugal force has been imparted to the wear pads, they fully engage the clutch drum housing so that the housing rotates together with the clutch pads or shoes and the hub and thus with the engine drive shaft propelling the cart rapidly forward. Such prior art centrifugal clutches have been manufactured and sold for years by Max-Torque, Ltd. of Melrose Park, Ill.
Some small motorized carts are sometimes used for racing purposes. Racing carts require close tolerances, differing centrifugal loading and different heat considerations. One of the prime considerations with racing clutches of this type is that of excess heat. Heat transfer between the clutch housing and the clutch hub can be significant. One of the weak links in such a clutch are the springs which can be subject to damage when temperatures increase to about two hundred fifty degrees fahrenheit (250.degree. F.) for example. In such a situation, the springs begin to anneal and can fail.